Conservation Terms

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As a custom framer, collector, or artist, there are many terms that relate to framing and conservation that are important to be familiar with. The following provides a useful reference list of key terms that apply to the preservation, restoration, or framing of art and documents.

Museum Quality Seal

Acid BurnFlatteningRag Board
Archival FramingHingingSpacer
BevelLipSurface cleaning
BleachingMat BoardUltralight Light
Center LineMat Board CoreUnmounting
CleaningMat Board OffsetVarish removal
Conservation FramingMouldingVarnishing
De-acidificationMounting BoardV-Groove
Dust CoverOverpaintingWindow

  • Acid Burn: Appears on artwork as yellowish or brown lines, typically due to acidic content of the substrate (paper) or acidic content of matting or backing boards that come into contact with the art. Often acid burn is associated with the use of non-conservation materials, and will appear as a “line” or outline surrounding the art (under the mat area) where the artwork becomes discolored and brittle.
  • Acid-Free: Paper, matting or backing materials that are pH neutral, meaning they are at or close to 7.0 on the pH scale. These products are neutralized either through to processing to neutralize the acidic content (alphacore), or through the use of inherently PH neutral materials such as rag mat board which is made from cotton. In order to be conservation quality, materials produced from wood pulp must be both acid-free and lignin-free, which is the case with alphacore mat board products.
  • Accretion: The accumulation of soil, e.g. fly specs, dirt, etc.
  • Archival Framing: Describes the framing procedure where all materials are completely acid-free. Also see Conservation Framing.
  • Bevel: The 45-degree angle cut that is made at the inside edge of a mat board window.
  • Bleaching: Removal of yellowing and/or stains from paper.
  • Center Line: The horizontal line that is halfway between the top and bottom of a work of art. In a wall arrangement of framed art, the center line bisects the entire grouping.
  • Cleaning: The process of removing of surface dirt or soil from art or documents, typically done by an art conservator.
  • Conservation Framing: The process of framing using processes and materials designed to protect and preserve valuable art or documents by minimizing the detrimental effects of natural aging. Conservation framing should be readily reversible so that the piece can be returned to its original “unframed” condition without damage.
  • De-acidification: The process of neutralizing the acidity in paper by alkaline washing.
  • Dust Cover: Paper which is placed on the back of a framed piece to help protect artwork from dust or insects. Typically, the dust cover is attached by applying ATG tape along the frame edges and adhering kraft paper or other backing paper to this.
  • Embrittlement: Weakening that results from acidity in paper and causes brittleness over time. This is very easy to see in old newspaper that turns yellow and becomes brittle quickly due to the acidic content of the newsprint.
  • Fillet: A very thin moulding used as an accent in framing. The fillet is installed inside of the mat opening, rather like a frame within a frame. Fillets are available in a variety of metallic, wood, and other finishes. Care should be taken to properly install a wood fillet by applying an acid-free barrier when it will come into direct contact with valuable art. Special fillet cutters are available to chop fillet moulding.
  • Flattening: Drying works of art between blotters or under weights after bleaching or deacidification.
  • Foxing: A freckle-like, reddish brown staining of paper that is caused by fungus and may result from the use of non-conservation quality framing materials. Foxing can be produced by a combination of high heat, high humidity, and natural salts.
  • Glazing: Refers to the protective layer of picture frame glass or acrylic (plexi-glass) used in framing to provide external protection to the contents. It is important to create air space between the glazing and the art itself, which is the main reason for choosing a mat or spacer bars to separate the art from the glazing itself.
  • Hinging: The attachment of art or a document to its museum backing board, using various methods including Japanese wheat paste, archival quality tapes such as Filmoplast P90, acid free corner hinges, or other approved methods.
  • Lip: The thin edge of the moulding that is just above the rabbet. The lip typically projects over the glass to hold it and the frame contents in place.
  • Mat Board: The material used to separate the artwork from the glazing. Typically the mat has a window opening to expose the art being framed. Mat board generally is made up of three layers: the face paper, the core and the backing. Mat boards come in a wide variety of thicknesses, quality levels, colors, and textures. See “acid-free” for more explanation as to quality considerations for mat board.
  • Mat Board Core: The center area of mat board into when a bevel cut is made. Mat board core is made with varying core thicknesses, with 4-ply being most common, and 2 ply, 6 ply and 8 ply also available.
  • Mat Board Offset: When one mat window is stacked on top of another in a double mat presentation, the offset is the reveal that shows from the bottom mat. A typical offset between the top and bottom mat is 1/4″.
  • Moulding: The material used to build a frame, which is cut on a 90 degree angle in four sections and joined to form a frame. Wood mouldings are the most common and popular choices, although mouldings can also be made from metal, plastic or laminate.
  • Mounting Board: The backing material which is used back or provide support to the artwork. Typically, the artwork is mounted to the mounting board, or hinged from the window mat opening. See “acid-free” for more explanation as to quality considerations for mounting board.
  • Overpainting: Previous repairs made by painting over damaged areas of a painting.
  • Profile: The cross section of a frame which illustrates the height, width, and rabbet of the frame. Viewing the profile of a moulding makes it easier to assess the look and proportions of a particular frame.
  • Rabbet: The inner channel of a frame which holds the picture and additional framing materials including the glass, backing, and mat.
  • Rag board: A board manufactured from cotton or other fibers. 100% Cotton or rag board was the only option for conservators for many years and is still considered a high-quality choice for conservation framing.
  • Relining: A method to strengthen an old canvas by adhering a new canvas to its underside.
  • Retouching: Filling in areas on an original painting that are missing paint.
  • Spacer: This material is intended to separate the contents of the frame from the glass or acrylic. Spacers can be created using strips of mat board or foam core, or there are commercially available frame spacers that can be cut and inserted into each of the four sides of a frame. Deep shadow box frames can be made using spacers to display objects.
  • Surface cleaning: Removal of surface dirt from a piece of art or document.
  • Ultraviolet Light or UV Light: Represents the range of invisible radiation beyond violet in the visible spectrum. UV wavelengths range from about 4 nanometers, on the border of the x-ray region, to about 380 nanometers. UV light is present in natural sunlight and fluorescent lighting, and can be damaging to art and valuable documents. For valuable documents and art, UV control glazing (glass) can be used to filter out the vast majority of these damaging rays.
  • Unmounting: The unglueing of a piece of art on paper which has previously been glued down.
  • Varnish removal: Removal of the protective coat of varnish from the surface of a painting.
  • Varnishing: The application of a protective coat of varnish to the surface of a painting.
  • V-Groove: A V-Groove is a thin channel cut into a mat board as a decorative element, typically appearing as a white line accent in the border area of a mat.
  • Window: The opening in a mat board to that is created to display the picture underneath.
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